Field of the Invention
The present invention relates to a technical field of a display, more particularly, relates to a light guide plate, a back light module and a display apparatus.
Description of the Related Art
Since a liquid crystal itself cannot emit a light, a back light module is an important component of a liquid crystal display for emitting light. The back light module is used to provide an illuminant having a sufficient brightness and an even distribution luminance to ensure that the liquid crystal can normally display an image. Currently, the display technology of the liquid crystal display has been very perfect, and the design on the back light module also has been greatly improved. In addition to the liquid crystal display and the liquid crystal TV, the back light module also can be used as an illuminant for other display apparatus, such as, a digital picture frame, an electronic paper, a mobile telephone, etc.
The back light module can be classified into a downright back light module and a side back light module according to positions of the illuminant. As for the downright back light module, the illuminant is just placed a rear of a light incident surface of a light guide plate, and the light from the illuminant becomes plane light from a plane light source after passing through a section of space and being diffused by a diffusion plate and mixed. As for the side back light module, the illuminant is often placed on at least one side of the light guide plate, and the light is coupled to the side and directed into the light guide plate, then formed as a total reflection inside the light guide plate and propagated forward. By destroying the total reflection condition, the light can be evenly irradiated from the light emitting surface of the light guide plate. Accordingly, the configuration of the light guide plate has an important effect on the light emitting effect of the back light module.
FIG. 1 is an illustrative configuration view of a light guide plate in the prior arts. As shown in FIG. 1, the light guide plate comprises an incident surface 1 for receiving a light beam, a bottom surface 3 connected to the incident surface, an emitting surface 2 connected to the incident surface 1 and opposite to the bottom surface 3, a side surface 4 opposite to the incident surface 1, and two rest side surfaces. In order to destroy the total reflection of the light beam inside the light guide plate, an optical screen element 5 is disposed on the bottom surface 3. The incident light is directed into the light guide plate and is totally reflected many times inside the light guide plate and diffused into all space inside the light guide plate. When the incident light reaches the optical screen element 5, the incident light is diffused by the optical screen element 5 and emitted from the light emitting surface 2 of the light guide plate (the bottom surface of the light guide plate is light proof). By adjusting the density of the optical screen element 5, the luminance of the emitted light can be evenly distributed on the whole light emitting surface of the light guide plate. An illuminant 6 is provided outside the incident surface 1 of the light guide plate. A reflection case 7 is provided on the illuminant 6. Reflection sheets are provided on the side surface 4 and the other side surfaces to form reflection surfaces. The light emitted from the illuminant 6 is directed into the light guide plate through the incident surface 1, and led out from the light emitting surface 2 after being reflected by the bottom surface 3 and the side surface 4.
It should be appreciated for those skilled in this art that the above illuminant may be provided on at least one side surface of the light guide plate. For the purpose of description, the illuminant is provided on only one side surface of the light guide plate as shown in FIG. 1.
The conventional display apparatus generally has a single display surface. Thereby the light guide plate of the back light module only can emit the light from a single surface, that is, from the light emitting surface, and cannot satisfy the requirement of the double-surface display apparatus.